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' JJA. PHQGTQR ELECTRICAL conpawssa Filed Nov. 6. 1924 I iNVENTOR i frequency service.

"' j "peripheral wall Patented free as, 1928.

A Y T massacno ssr'rs, ASSIGNOBLIOL WIRELESS; BosroN, masssonosnrrgea conrolmnon assessment cormsnsnnn Application filce'tlovcmber 6 i924. SerialNmYSfiOOf- 4 This 'im'entionr'relates to 'ii'nprovements in electrical condensers or capacitors of the type involving high potential difi'erences between dilierent parts of the device, and more especially those operated at high fre qucnciesaas a; radio communication.

Among the objects ofthe invention is that of reducing heating of high potential in- .sulating material employed, 'and thereby pre-, l9 ven 'in'g deterioration, breakdown and" destructmni of such insulation. I

The invention consists or nientsjwhich are illustrated in thedrawings (which are about one-half scale)- and del scribed in'thc tciit, by way of example, in a present-day commercial high potential mica condenser, especially one adapted for high v Figure lis a side elex' atiom partly in seci 'ivention; and i a p i Fig; 2 is a sideelevationot the same i My present invention may be used alternatively with that of my application Serial No. 680,12l, filcd December 12, 1923, but is j preferable thereto,- largely by reason of retion, of a complete condenser embodying the\ h l A lead ;;and l dispense also with t e metal io duced cost, but, also by wayof improved oporation.-

The improvement hereof is on the type oi :condenscr which includes a metal enclosing casing MC to which the condenser S; Stis grounderhthe metal casing having -an openinmshown at the top 1) out through which extends high potential lead L. In this type, there is 'freqn'ently a potential difference of many thou'sandsot volts between high potential lead L and A of the-v casing, opening for said lead i. e1, the part o'f-the metal casing nearest said" lead. The practical problems involved in the construction of such condensersrelate' largely to provisions for the proper insulation oi'the high potential load trom the metal casingto, which the condenser is grounded,-.,andv provisions lor reducing the heating ofthe insulating mialerial used to separate the-thigh potential glead fronrthe metal casing.

v The nvention of my said priorapplicm tion was an advance upon pr or methoc s of grounded casing-1 and high I insulating the potential lead. -Themethod flush previously in us had involvedrthe surrounding ot the" high otential lead with an insulating the arrangcvwas located adjacent the structure extending substantially from the condenser stack to a considerable distance i outside of and beyond the 'ca-sing,- in general accord with patent to Priess, 1,596',374 but suchinsulating structureeonsisting of layers of mica sheets, and said built-up, mica structure resnltingqin high heat losses liable-to injure orl destroy the structlireitself. By use oi} the invention of my said'prior ape plicat o I dispensed with alloi saidina sul'ating i 'structure, save onlf a mica compare insulating, member. 18 of sa d Patent 1,596,374) serving as cover "forjthe opening 1 through the casing potential lad. p p

Bythe piment inventioml dispense with all insulating; material (as 18 of Patent 1,596,374!) liable to be harmfully heated and. located directly across said casing opening between metal casing and high potential structure of w my said prior invention which p mica diskcover. The type of condenser on WhlCh the present invention; is an improvement usually comprises a-metal casing I MG enclosing the stack of sheets ofiimica and metal foil, the stackbeing. grounded-to themetal casing, and the casinguhaving a top" opening for the passage. of. the high potential lead of the condenser. The type also usually has a static shield (as 24 of said Patent 1,596,- 374) cooperating with metal casing'MC, located outside the casing and connected to the high potential terminal. This type of condenser also usually comprises an embedment X ofparafiin wax or the like surrounding condenserstack S S and molded in the metal casing {injan inye'rted position). after the condenser stack is assembled in place inside thecasing; andthc casing may be provided with a bottom openingwhich, 'atterthe operation of wag: filling, is closed permanently by a metal bottomfMB screwed to the bottom of" the side wall ofthe metal thereof; by clamping members MGR/one at eachfend of the condenser stack; andby Y screws W passing through the casing walls. The casing is usually oblong (Figs. 1 and 2), in general correspondence with the oblongfstack which lies horizontally therein; but-ythe casing jmay'havw other sha es, as

' of the casing.

- being curved i circular, square or lozenge shape. The conalthough it is not as good a dielectric medidenser stack may be of any suitable construction, but usually consists of mica sheets as dielectric and metal foil sheets as armatures; also preferably, for high potential working, the condenser st ck consists of a plurality of sections conne-ted in series. In the case shown, and preferably, the stack consists of two portions S S arranged end to end, and each comprising a plurality of seriallyconnected sectioiis; and from the midpoint of such stack the high potential lead L is connected. i

The structure of the present improvement is very simple, but its increased value over that of the invention of my said prior application is measured by its high economy in cost and its improved operating efficiency in reducing heat losses and the consequent permanence of the insulation between the grounded metal casing and the high potential lead.

The structure consists primarily of the inverted bowl-shaped cover C of insulating material as glass, and, secondarily, and in combination of the metal static shield B ofshape corresponding to said bowl-shaped cover which is nested in protecting shield B. The rim of the inner bowl C rests on a ledge A at the peripheral wall of the lead-opening A locking recess R is formed in the metal casing above said ledge A, and 51c radially extending flange E of the rim of bowl C is held permanently to casing MG by fusible metal or-Portland cement 'or the like FM cast in said recess R, said recess at its outer periphery shown for the purpose of retaining the hardened casting. Bowl C is preferably of glass, such as any form of oven-glass withstanding high temperatures without cracking, and I prefer to use the glass sol under the name ovenglass as an efli ent material standing abrupt and unequal: changes of temperature at several hundr d degrees Fahrenheit. While the invention pro ides means for reducing heat losses verymaterially, yet the wax processing of the device involves such temperatures making desirable the'use of highoven-glass exposed to the hot wax.

As shown in Fig. 1, the open end of bowl C is in full and free communication with the interior of easing. MC, and closes the lead opening so that, after the bowl is socured in place and the entire structure invcrtcd for wax filling from the bottom casing opening, the wax filler will fill the interior of the bowl around high potential lead L as the latter passes centrally through the wall of the bowl C. Thus no insulating material. other than wax or the like is present directly across the top casing opening from wall to wall'thereof. The only insulating material there which is not seriously injured by heating,

resent is the wax,

um as air; the wax being cmploycd in condensers of this type for the purpose of protecting the condenser stack from moisture,

The outer diameter of bowl (J preferably and usually is substantially less than the longer inside diamctcr ot the casing itself, being conveniently, in the instancc'oi the oblong casing shown, a little less than the shorter width of the casing: and thc cmbcdding material X in thc hollow intcrior of cover C, lies between all points of high potential lead L and the nearest portions of the metal casing, the bowl shape of cover C permitting the omission from bctwccn the casing and the high potential lcad L of all insulating material liable to injury by high heating, as distinguished from the case of an I insulating disk covering the top casing opening and lying in the path of shortest dis tance between the metal of the casing and the high potential lead. The inner diameter of bowl C at its rim, (which contains cmbcdding material X at the location of shortest distance between casing and lead L). although usually smaller than the longer diameter of the casing, yet should be as la rgc as convenient without unduly increasing need of excessive strength of the glass bowl. And the depth of the bowl may he considerable, for the purpose of increasing the leakage distance, without being so great as to increase unduly the over-all dimensions of the entire structure.

The static shield B is, according to this invention, made bowl-shaped to correspond with the bowl shape of gla'ssicovcr (l, being separated therefrom by air as a perfect dielectric. That is. the flat disk static shield 24 of said prior Patent 1.596.374 is modilicd to a bowl shape to adapt it to insulating bowl C. The rim of bowl B extends downwardly to within a desired distance of the metal of easing MC, and is there flared or rolled at F to prevent high tension brushing. Metal bowl B at its up )cr portion is electrically connected to the high potential termiml, and its lower roximity to metal casing MC serves to con no the lines of electrical stress largely to locations outside of'glass bowl C, and cause such lines to exist in air dielectric, thereby preventing heating of any solid. dielectric material. The intensity of the electrostatic field between casing MC and the high potential lead L and condenser terin nal U 1s a function of the operating voltage and frequency. Condensers with the due heating. This invention,bymeans of the bowl-shaped cover B over bowl G, permits omission from the most intense part of the electrostatic field, of all insulating material liable to be injured by heating; and the provision ofnietal bowl B outsideof glass bowl Z'field from passage throughfthe insulating shape and location of shield B, and the material itself of cover C, all co oper'nte to the C and approxiniat-ingto metal casing'MC, 'resultsrfurther in 'directingthe most intense material of bowl. C. Also, the use of ovenglass for the bowl-shaped cover C permits- ,the use of voltages and frequencies, Without injuring cover Qflwhich may resultjn quite Y intense fields through -cov er G notwithstand, "ing' the provision f'field shunting bow-l B.

Thus the shape end location of cover C, the

end o t grent-ly increasing the upper limitsof permissable operating voltage and frequen- .gci es. ,The bowl shape ofipzirts B and Gina be more' or less shallow than as shown in Fig. 1,. for ditfereiih designs for varying conditions of service This bowl sha pe howe'veif, is'of 'value in greatly. increasing the -c'reepage distancebetween the h gh etential.-lead 'nnd terminal and thefpoints on shown as to provide a. definite safety spark gap and insuch case it provides the greatest extent ofmechanicul protection for the insu "lilting materials as glass, of bowl C.

electric loss.

'inetal casing MGwhich are nearest thereto; andthe use of glass {is-the insulating nate5 l mini for bowl C, jo rovidesia smoothsurfacere- 5 ducing li-ubility to flash oven, Also the use of any kindofaovenglass fot bowl G pro- I vides a ;surtace which is less attacked by .inoisture 31nd atmosphere than ordilfmiy glass Oven glass has a desirably, low di Also the rim ot-bou'l B ,may.

extend so elose to the :inetal of casingMC, as

--"With the use of bowl C as ulstmguished from the use of a fiat disk to closethe lead open ng of the casing, there is no direct lmo the cise of the use of a built-upstructure of lvidcs an equally lon'g crecpage pathof much dwoen the uppeizpa rt 'of such shield and a" I radial extension from terminal U, insteadof- ,loss structure cost'.

of (reopen-e between casing andfhigh potential'lcad. but, on. the otherhzind, there is a very longereepage PillZ-lhiDOilSlll'Qd by the, depth ofglass bowl C, between the metal casing to which the edge of bowl C is secured,

and theclosed end of the bowl C through which the'high potential lead extends. In

mice sheets s rrounding high potential lead L, it was c nsidered necessary to guard against oreepzigeby the" provision of a stag-- gered path uplland down the'insuluting struc ture The bowl shape of my cover C proat erirn'of B as shown he cost of ,"production?pldinly is much-- less than that of the metal interior construe tion of my said prior'applicationffor 'pl tent; and very inuch less thanthe prior practice of surrounding the high potential lead with perinit passage of St U- f'be seen froinithe above; r

a builtmp structure ofv mica sheets. The glass bowl C may be produced in large uantitiesat uve'ry small cost pcr unit. In act, the shape ofglass bowl C is substz ntiss ally the saine'as the 'doni'estic baking cups 76'. made 'of'oven'glass and now on sale,'sa-ve thatthe top bf bowl G (Fig-.1) is perforated to permit passage of the high potential terminal Ugimd it is quite practical. to use. such baking cups in my in\'ention,'but"so N ,peiforzited'; In short, the bowl-shaped cover of this invention is a most economical as well as eflicient substitute for the prior high potential insulators which consisted of the built up insulating. structures of the 80 prior art, or ofthe micadisk co'ver'of my said prior application fdrpatent' with its vaocompaxlying centnel metallic structures.

In the construction: illustrated, bowl C .se 'ves as thefsupport for the highpotential termin l}; and for the metal shield 'B. In.

this constructionythe lead L between; the ;conde nsei stack andthe top high potential-- -.terininal U, n1aybe 2i flexible lead soldered thitough/bothbowls C and B; each of which"--' has its closed end perforated foithe purpose. ,Stud U is threaded throughout itsslcngth as s basisijfor assembly of the following parts beginning from the bottom; A" hex nut l ..brll$. up against inetal Washer 52, which bears up against lower gasket 3, "(which bearsup against the glass wall of bowl (1' Gasket 3 may be ofloather, lead or rubber to (listributcthe stxainsfoveiy the 'lzhiss oi bowl fil andpievent cracking thereofby'thw highpressui'e of assembly. lbp'er gasket 105. 4, of the T-shaped Cross section "shown,

enters into the hole in bowlG and sepurz tes the inner sllof said hole from metal stud U; this gasket i-also bearing against the top of the elosed end of bowl C. and being of material like gasket 3 to distribute 'mebhanicel strains over the glass. TMetnl'wzisher 5 is held down on gasket 4 by nut 6. [Above nut-6 is a metal Washer 7 of" larger diometer'which supports the uppel fiat part of shield 13. Shield B is ..l\ere erfor ate'd to y H bove Bjis a .wa'sher 8 held down by nut 9.1 .Qntop of nut'9 isxa lock nut 10. On topofymtlO are two washersll and 1-2 between which may 1530 be clamped the circuit lead, by incans of a nut 13, on top-of which may bes lock nut.

' if desired to .pleVLllli bucking on of nut '13 unden vibration. .The ease o'i usseinbly will 7 3 The" low potenliitlaleud for the-chicuit, in

wh ch the condenser may be-usedmay beat- :taohed to any dcsired part of metal casing Magi such as integral supporting-lugs Z.

prior constructions, the rigidityiof the we high potential lead and terminal have been obtained by an extension of the stud U down to the condenser stack, and such high potential stud has been employed as a heat-conducting path, for the purpose of conducting heat to the outer atmosphere but incidentally Contributing to the heating of the insulating structure surround lg such high otential stud. Here, however, the lead L From the condenser stack to the high potential terminal may be the flexible lead L shown, because the rigidity of the high potential terminal U is maintained by bowl (I. the rim of which is supported on metal casing MC; It is not always advantageous to connect a rigid high )otential lead to the condenser stack, and by this invention, therefore, it is permissible to use the more convenient lead in the form of the flexible cable L.

Another advantage of the bowlshaped insulating cover C is that the shape of shield 13 and cover C may be assimilated to one another so that when cover C is located as shown inside of or nested with shield B, said shield serves to deflect the mostiintense field from the insulating material of which cover C is composed; that is, as distinguished from the case ofa fiat insulating disk closing the top of the lead-opening of the casing, here the shield B can be given the above useful function in connection with bowl cover C by giving to the shield a bowl-shape gen- 4 erally conforming to the shape of coverbowl C. In the form shown, both insulating cover C and shield 13 have been altered in shape from prior designs, in order to conform to one another, which results not only in a shunting of the field from the material of cover C, but constitutes a much longer cree age path along the insulating'material of the cover and between the high potential terminal U and metal casing MC, than in the prior case of an insulating disk cover.

The exigencies of heating by electrostatic 'fields, involved in the subject-matter hereof, is due largely to the small over-all volume of the high potential condenser in question, in connection with the disproportionately. high potentials and alternating frequencies to which the device is subjected in service.

Of course, if desired, the side wall of glass bowl C may be corrugated to increase yet further the leakage path; but that is not usually necessar as there is nothing to preventincrease of? leakage path wherever delsjg'etll, by simply increasing the depth of the It is to be understood that the invention is not limited to the embodiments and features specifically shown and described herein, but that such embodiments and features are subject to changes and modifications without any departure from the spirit of the invention. Clearly, although the bowlshaped members are preferably and usually of circular form, they may have any other desired section while yet retaining their substantial bowl shape.

I particularly point out and distinetl y claim the part, improvement or combin'ation which I claim as my invention or discovery, as follows 1. In a high potential electrical condenser of the type wherein the condenser is embedded in insulating material inside an enclosing casing of metal to which the condenser is grounded. the casing having an enclosalrle opening to permit filling the casing with the embedding material and the casing haying an enclosable opening for the high potential condenser lead, a static shield of metal being connected to one terminal of the condenser and extending toward the other, the improvement which comprises a bowl-shaped member of insulating material as a cover'for the lead-opening of the casing, and having an external diameter less than the internal diameter of the casing, and insulating cover being located inside and surrounded and protected by said shield and having its rimvsecured to the wall of the easing lead-opening-and supporting said shield and secured to the high potential lead.

2. In a high potential electrical condenser of the type comprising an enclosing casing of metal to which the condenser therein is grounded, the condenser having an opening out through which extends the high potential condenser lead, and a static shield of metal electrically connected to one condenser terminal and extending toward the other, the improvement; which comprises a. bowl-shaped member of insulating material as a cover for said casing opening, said bowl-shaped cover surrounding the high potential lead and being surrounded by the. static shie1d,'said insulating cover having its rim secured to the wall of the lead opening of the casing. v

3. In a high potential electrical condenser of the type wherein the condenser is enclosed by a casing of metal to which it is grounded, said casing having an o ening for the high potential condenser lea the inn provement which comprises a bowl-shaped cover of insulating material for said opening, said casing around its said opening being ltlt) constructed with a locking recesstol receive other condenser-terminal bowl being of insulating material and having improvement which comprises two generally howl-shaped members nested together out-- its rini'secured to the wall of and closing the casingepening and the outside static shield bowl irovhlin mechanical rotection for the insulating material of the inside bowl.

5. In an electrical condenser of the type wherein the condenser is enclosed by a casing of metal to which lt s grounded, said cas ing having an opening tor a condenser lead,

- the improvementwhich comprises a bowlshaped cover of insulating material having a radially-projccting rim resting on the oils ing around said lead-,Aopening and having a perforation through its closcd end for the high potential condenser lead, the hollow interior of the bowl having free connnunication with the interior of the casing; the radially-projecting rim of thebowl being secured to the casing by a locking casting in the casing; and the closed perforated portion of the howl being separated by a yield i'ng gasket from thecondenscr lead.

(8. In an electricalcondenser, the combination .with an enclosing casing of metal having an opening for a, terminal-lead of the condenser, of two substantially howlshapcd members nested together outside the casing and having their cavities facing the casing; the outer howl being of metal and the inner bowl of insulating material; the rim of the inner howl beingsecured to the casing' around the terminaldead-opening thereof and closing said opening; the outer bowl being electrically connected to the ter- .minnllead and extending over the inner bowl and proximate the casing; the inner howl being perforated to permit -passage of the terminal-lead to the outer mwl: the outer bowl being mechanically supported by the inner bowl; and the. inner bowl being mechanically secured to the terminal-lead.

7. In a high'potentia-l condenser of the type wherein a casing of metal surrounds the condenser itself and. 15 connected to the contained condenser as a terminal thereofim,

said casing having an outlet opening for a projecting terminal-lead of the condenser, the improvement comprising two generally bowbshaped members nested together and surrounding the projecting terminal lead outside the casing; the inner howl being of insulating material, closing said opening and having its rim secured to the portion of the casing which surrounds said opening; said inner bowl having its open-end facing the interior of the casing and its other end pertorated to permit passage of the projecting terminal-lead to the outer bowl; the insulating material of the innerfl'bowl lying substantially outside the space of shortest distance between the metal casing and the projecting terminalrlead; and the outer bowl being of metal, electrically connected to the projecting terminal-lead and extendin toward but not, electrically connected wit the metal of the casing and thereby providing electrostatic and mechanical protection for the insulating material of the inner bowl.

8. In a high potential condenser of the type wherein the condenser itself is enclosed by a easing oi metal interiorly spaced from the condenser and having an opening for a projectin terminal-lead of the enclosed condenser, tie'space. between'casing and con-- denser heing'filled with an embedding insn-. lating material which is hot and fluid when introduced, the improvement in insulating the casing from the projectingterminal lead which consists of a generally bowl-shaped cover closing the casing opening, located outside the casing but having its cavity facing and in communication with said interior casing-space; said opening and cover ,having diameters which are short relative to the superficial dimensions'of the corresponding face of the casing; and said cover being perforated to permit passage of the projecting terminal-lead and consisting of electrically insulating oven-glasswithstanding the heat of the initially fluid embedment.

JOHN AI BERT PBOCTOB. 

